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A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.. In POSIX extended regular expressions, there are 14 metacharacters that must be escaped — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ...
/ is special because it indicates the end of the regex. For example, insource:/yes/no/ is treated the same as insource:/yes/ no (because the keyword search for no/ ignores punctuation). The / character must be backslash-escaped everywhere it appears inside a regex – even inside square brackets or quotation marks.. matches any single character.
It can signify exponentiation, the bitwise XOR operator, string concatenation [citation needed], and control characters in caret notation, among other uses. In regular expressions, the caret is used to match the beginning of a string or line; if it begins a character class, then the inverse of the class is to be matched.
A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
Brackets: Angle bracket, Parenthesis • Bullet: Interpunct ‸ ⁁ ⎀ Caret (proofreading) Caret (computing) (^) Chevron (non-Unicode name) Caret, Circumflex, Guillemet, Hacek, Glossary of mathematical symbols ^ Circumflex (symbol) Caret (The freestanding circumflex symbol is known as a caret in computing and mathematics) Circumflex ...
In SGML, HTML and XML documents, the logical constructs known as character data and attribute values consist of sequences of characters, in which each character can manifest directly (representing itself), or can be represented by a series of characters called a character reference, of which there are two types: a numeric character reference and a character entity reference.
left square bracket with quill; right square bracket with quill; u+2045; u+2046; ps, open; pe, close; ... caret insertion point u+2041: po, other common ⁂ asterism ...
Regular Expression Flavor Comparison – Detailed comparison of the most popular regular expression flavors; Regexp Syntax Summary; Online Regular Expression Testing – with support for Java, JavaScript, .Net, PHP, Python and Ruby; Implementing Regular Expressions – series of articles by Russ Cox, author of RE2; Regular Expression Engines